1. Field of the Invention
This invention relates to a welding gun and, in particular, to a miniature welding gun.
2. Description of the Related Art
A goose neck metal inert gas (MIG) welding gun generally comprises a handle, a wire feed mechanism, and a torch gun or barrel. The welding gun typically also includes a gas tube for supplying inert gas to the end of the torch barrel. Some welding guns also include a water tube for supplying cooling water to the end of the torch gun or barrel. “Push-pull” MIG welding guns typically also include motor for driving the wire feed mechanism.
There are three general types of welding guns: pistol grip, goose neck and in-line welding guns. In a pistol grip gun, the motor is located below the wire feed mechanism within a handle and lies along an axis that lies generally perpendicular to the longitudinal axis of the gun. In contrast, in an in-line gun, the motor lies along the longitudinal axis of the gun and is positioned generally behind the wire feed mechanism. A goose-necked gun includes a curved torch gun or barrel. In some arrangements, the welding gun is configured such that the operator can change the angular position of a curved barrel relative to the wire feed mechanism.
A MIG welding gun typically also has a contact tip that preferably performs two functions. First, it accurately guides a weld wire to the point of contact with the workpiece. Second, it conducts adequate current, which may be as high as 400 amps or more, to the weld wire. To achieve those results, a relatively long contact tip made of copper can be provided. The contact tip can have an axially extending hole provided therethrough. The hole preferably is sized slightly larger than the diameter of the weld wire. Typically, the outer diameter of the weld wire is about 0.004 inches to about 0.020 inches less than the diameter of the hole. In one common embodiment, the weld wire outer diameter is between 0.008 inches and 0.012 inches less than the inner diameter The contact tip can be coupled to and extend from a gas diffuser, which is in communication with the gas tube. In this manner, an inert gas can be directed around the welding arc through the gas diffuser. Current can be supplied from a power block and then through the torch barrel and to the contact tip.
In general, welding guns are used by professional welders in many industrial applications. To meet the demands of these industrial applications, welding guns are typically relatively heavy and bulky instruments. Nevertheless, there is a general need for a smaller, lighter welding gun that can be used in non-industrial applications. For example, such a smaller, lighter welding gun may find utility in emergency, hobby, home or recreational environments. It would also be advantageous for such a smaller, lighter welding gun to also be a “push-pull” welding gun because of its generally superior performance, especially when welding with aluminum wire. Despite this need, efforts to date to develop a smaller, lighter welding gun for emergency, hobby, home and/or recreational uses have not been satisfactory.